Non-coherent source of ultraviolet
radiation capable of producing quasi-monochromatic radiation from the near UV
(λ = 354 nm) to the vacuum UV
(λ = 126 nm). The operation of the excimer lamps relies on the radiative decomposition of excimers
created by various types of discharges.
- Using noble gas, halogen, or noble gas / halogen mixtures with fill pressure ∼ 30 kPa, the radiative @D01547@ of the @E02242@ or the @E02246@ produces nearly monochromatic radiation. Some of the commercially available wavelengths for the particular excimers or exciplexes are 126 nm with Ar2, 146 nm with Kr2, 172 nm with Xe2, 222 nm with KrCl, and 308 nm with XeCl, obtained with efficiencies of 5-15%. Pulsed Xe-@E02242@ (Xe2) lamps may have up to 40 % efficiency. Good efficiencies are also obtained with XeBr at 291 nm and with XeI at 253 nm. Other wavelengths produced with much less efficiency are 207 nm (KrBr), 253 nm (XeI), 259 nm (Cl2), and 341 nm (I2) (see Table 1).
Table 1: Peak wavelengths (nm) obtained in dielectric-barrier discharges with mixtures of noble gas (Ng) and halogen (X2). Wavelengths of commercially available lamps are shown in boldface type. The molecular species indicated are excimers or exciplexes.
| ||X2 ||Ne ||Ar ||Kr ||Xe |
|Ng2 || || ||126 ||146 ||172 |
|F ||157 ||108||193||249||354|
- Phosphors are used to transform the UV radiation into @VT07496@ radiation. This is the basis of mercury-free fluorescent lamps and of flat plasma-display panels with a large screen.
PAC, 2007, 79, 293. 'Glossary of terms used in photochemistry, 3rd edition (IUPAC Recommendations 2006)' on page 335 (https://doi.org/10.1351/pac200779030293)